Now that DOOM Classic has been released on iTunes, John Carmack has written his development notes on the project which you can read here.

This week we took some questions for John from the id Software twitter feed, and you will find his answers after the jump.

Khct: What was the most fun and/or rewarding part of developing DOOM Classic?
Porting a game is a very different experience from developing a new game. With a port, after working for a while, there is a moment when BANG — the game is there. After that, it is mostly a matter of fixing problems, optimizing, and polishing the experience. This project was especially rewarding because I felt that I was being extremely productive on the days that I was working on it — I was probably the best person in the world to do that work at that time, and I was knocking out issues left and right.

Matthaigh: Did you encounter any problems when porting the code to iPhone/touch? Such as APIs you used?
It went very smoothly. The prBoom codebase that I based it on already compiled for OS X, so there wasn’t much grunt work, and I had all the device specific IO code that I developed for Wolfenstein Classic. Being able to take advantage of the GPL code that other people have maintained and improved over the years has been very satisfying for me. I always argued that we got worthwhile intangible benefits from my policy of releasing the source code to the older games, but with Wolfenstein Classic and DOOM Classic I can now point to significant amounts of labor that I was personally saved. In fact, the products probably never would have existed at all if my only option was to work from the original “dusty deck” source code for the games. If we were even able to find the original code at all. Hooray for open source!

Seventhcycle: What sort of synth did you use for DOOM Classic’s music? It sounds like AWE32 or AWE64. Why not use something like a SDD4?

The following answer is from Christian Antkow, Aural Assault Technician, id Software

Where possible, I pulled Redbook Audio off Bobby Prince’s archival CD’s and I can only assume it was created with a Creative AWE32 or some other comparable relic back in the day. Where I did not have original Redbook audio to work with, I went back to the original MIDI’s and ran them through a modern Creative X-Fi General MIDI module in an attempt to match the original Redbook audio as closely as possible. My original intent was to use the East/West Colossus Virtual Instrument in my DAW, and run all the MIDI through their GM instruments to generate completely new high quality renderings. When I did so with the first couple tracks, it just sounded way too “real” and all sense of nostalgia was lost.

So, that’s really the main reason I didn’t redo everything in a modern instrument. All sense of nostalgia would be lost and I felt that needed to be retained.

Kevinquilen: After all these years, how do you feel that people are still interested in DOOM and Wolf 3-D up against newer games?
Nostalgia undoubtedly plays a part, but I do think that the games hold there own and then some for playability. The iPhone market is full of titles that are heavy on aesthetics and light on quality gameplay. There is a LOT of gameplay in the old titles, and I spent a significant amount of effort to make sure that they play well on the new platform.

Thanks to all of the Twitter followers who submitted their questions, and of course John and Christian for answering them!

I know what you mean, I liked Duke3D with DukePlus and the HighRes pack, it was just as nostalgic but added a new depth of gameplay in. But even without it the replayability and modern gameplay factor still hold up beautifully.